She was a young rising star in the banking world. He was a dapper Wall Street financier with a fortune to invest.

Lori Finkel was 30 years old and managing director of the leveraged-finance group with BT Securities Corp. when she met billionaire financier Ted Ammon.

“He was my client and I worked on his transactions,” she recalled last week.

It wasn’t long before the green-eyed blonde, an expert skier who is fluent in French, and the wealthy, married Ammon became “very good friends” – and then lovers.

Over the course of their 10-year affair, Finkel and Ammon would rendezvous as often as twice a week, she has revealed. They had their last tryst in his East Hampton bedroom just hours before Ammon was bludgeoned to death on the same bed.

The tale of lust, adultery and murder makes a startling contrast to Finkel’s outward image as a successful businesswoman and mom.

Finkel, now 42 and managing director of Credit Suisse First Boston in the bank’s New York division, spoke a year ago at a Wharton School conference on juggling career and family – “the tricky business of balancing work and life outside the office,” the agenda said.

She has held a string of high-powered positions at major banks and impressed colleagues as “bright, aggressive and talented,” as a male colleague described her.

She has also amassed her own fortune – she owns a $1.8 million home in the tony Hamptons hamlet of Water Mill- a short drive in her Land Rover or on her Piaggio motorcycle to Ammon’s estate.

A childhood friend, who spoke on condition of anonymity, told The Post, “She was always at the top of her class. We knew she would be famous one day.”

Finkel was called to testify in the trial of Danny Pelosi, who is charged with killing Ammon in October 2001. Pelosi was carrying on an affair with the financier’s estranged wife, Generosa.

Finkel was one of four siblings growing up in Edison, N.J. Her father was a prominent obstetrician, her mother ran a baby-knitwear company.

Lori had a “brilliant mind” and lots of pals, the friend said. “Lori never had to study but always got an A-plus on the test. She was just naturally gifted in every subject.”

Finkel attended the private Fieldston School in Riverdale. In New York, she honed her flair for fashion – and developed a taste for designer clothes, the friend said. Finkel went on to Brown University, earning a bachelor’s degree in economics and art history. Within a year or two of graduation, she landed a plum job as vice president at Drexel Burnham Lambert before joining BT.

Within a few years of meeting Ammon as a business client, she said, “we were intimately romantic.” Their trysts continued “on and off” – at times as often as twice a week, but sometimes not for a long while.

Finkel was apparently no secret to Ammon’s wife. A former nanny for the Ammons testified Tuesday that Generosa told her children that Ammon had a kid with Finkel. Finkel was not asked about that on the stand.

She has a child with Andrew Cogan, the CEO of Knoll Inc., and the son of Wall Street legend Marshall Cogan, former owner of the ’21’ Club.